In the oil and gas industry, once a hydrocarbon field development has been fully planned and contains a set of platforms that will hit all or most (depending upon engineering and geographic constraints) of the drilling targets, it is often desirable to investigate how many fewer targets would be hit if less platforms were used in the development. A platform is said to hit a particular drilling target if a well is planned from that platform to the target. Each platform will have a drilling template or a slot template, which represents the number of locations from which to drill the wells. These locations, called slots, determine how many wells can be drilled from the platform. How far from a platform a target can be hit by the platform represents the reach. There is generally an absolute maximum for a particular hydrocarbon field development, but each target may also have a maximum effective reach due to its depth and the engineering constraints on the type of well planned for that type of target.
Consequently, there is a particular cost associated with each platform and, depending upon the environment, type and size of the platform, this cost could run from the tens of thousands to millions of dollars. Likewise, there is a particular value associated with each target hit by each platform within a particular development scenario. Development scenarios contain different configurations of platforms and targets, which contribute to an overall value for the scenario. When planning the hydrocarbon field development, there will often be a preferred number of targets. If a platform adds fewer than the preferred number of targets to the scenario, then the value of the scenario is greater without the platform.
The objective in hydrocarbon field development is then to identify the platform that will least impact the number of targets hit, remove the platform, re-plan the scenario without the platform, and proceed to the next least valuable platform until such point where removing the next least valuable platform would cause the scenario to drop below the preferred number of targets. In a relatively small field, with only a handful of platforms, this job can often be done visually. On the other hand, in a large field with tens to hundreds of platforms, it is both difficult and tedious to even look for possible candidates for removal, much less to do a thorough evaluation of them.
In U.S. Pat. No. 7,200,540, which is incorporated herein by reference, workflows are described for generating well path plans, and the resulting platform locations from selected well targets. The workflow described in the '540 patent begins with using any of three methods to arrive at the possible platform locations. The workflow then verifies that the platform location is in a geographically valid area. The actual platform locations are then determined by the “find best new location” algorithm and adjusted with the “optimize platform locations” algorithm. Either of these algorithms may use the “count reachable targets” algorithm, which determines the number of targets that may be reached and the total distance to reach the targets for a given set of platforms.
The techniques and workflows described in the '540 patent, however, fail to address identifying and removing the least valuable platform(s) in order to reduce development costs while keeping as many of the preferred number of targets that were previously hit by the removed platform(s) as possible. In other words, the conventional techniques and workflows merely determine the best locations for a fixed number of platforms.
There is therefore, a need for determining the optimum number of platforms to be used in a hydrocarbon field development and their position.